Telephone system



Oct. 6, 1942. E. L. ERWIN TELEPHONE SYSTEM Filed March 16, 1940/NVE/VTOR E L ERW/N 27mm/Di Patented Oct. 6, 1942 TELEPHONE SYSTEM EdsonL. Erwin, Towaco, N. J., assgnor to Bell Telephone Laboratories,

Incorporated, New

York, N. Y., a corporation of New York Application March 16, 1940,Serial No. 324,306

15 Claims.

This invention relates to telephone systems and particularly totelephone systems in which connections are established automatically.

An object of the invention is to improve and simplify such systems andto economically utilize the required equipment.

Heretofore systems of this type have been arranged with commonrecorders, marking circuits and linking circuits for establishingconnections between subscribers lines and between trunks and subscriberslines in which idle links and registers'are seized and controlled by acommon marker circuit to effect connections after which the recorder andmarker circuits are reverted to common use.

A system to which the present invention is ap. plicable has beendisclosed and fully described in a copending application of E. L. Erwinand F. R. Lamberty, Serial No. 325,510, led March 23, 1940. This systemcontemplates the use of call originating switches of the cross-bar typefor establishing connections from calling lines to linking circuits andof call terminating switches of the same type for'establishingVconnections from said linking circuits to called lines, that'is, allthe lines appear as calling lines on call originating switches and ascalled lines on call terminating switches. Thus when a call is made aselect magnet in a call originating switch is operated followed by theoperation of a holding magnet to establish a connection from the callingline to a link circuit and when the call is extended to the desiredcalled line a select magnet in a call terminating switch is operatedfollowed by the operation of a holding magnet to establish a connectionfrom said linking circuit to the called line.

In the foregoing system it is a feature of the applicants invention toarrange the marker circuit for establishing connections betweensubscribers lines so that when a holding magnet in a call originatingswitch is operated, a holding magnet in the associated callfterminatingswitch where the calling line also appears as a called line is operatedand when a call terminating switch is to be operated for establishing aconnection to a called line, the holding magnet in the associated calloriginating switch is first operated followed by the operation of theholding magnet in the call terminating switch, thus both holding magnetsare always operated in a call originating switch and the associated callterminating switch regardless of which of the two switches are used toestablish a connection. The purpose of this arrangement is to simplifyand improve the operation of the control circuits for the switches.

It is another feature of the present invention to utilize these holdingmagnetsfor a calling subscriber lock-out arrangement whereby if thecalling subscriber fails to dial within a certain time interval afterdial tone is received or fails to complete the dialing during thisperiod, the call originating switch is released and the callingsubscriber is locked out or prevented from originating another callunless he rst replaces the receiver. The arrangement is such that whenthis time interval has elapsed, a permanent signal is received causingthe release of the holding magnet in the call originating switch whichcauses the operation of the calling subscribers line relay which in turnlocks the holding magnet of the associated call terminating switch andthis latter holding magnet being maintained operated now controlscircuits that prevent the line relay of the calling subscriber fromoriginating a second call.

' Itis another feature of the invention to utilize these holding magnetsfor the establishing of revertive calls on party lines. The arrangementis such that when a subscribers station is called which is connected tothe same party line as the calling subscribers station, the calledsubscriber is rung by the designated code ring and when the subscriberanswers, the holding magnet of the call originating switch is releasedto release the established connection and this magnet in turn causes theline relay of this line to operate and hold vthe holding magnet of thecall terminating Vswitch operated to maintain the line busy as in thecase of the lock-out arrangement described.

This invention has been illustrated in the accompanying drawing in whichFig. 1 shows in diagrammatic form the general switching plan employed inthe above-mentioned copending application and to which the presentinvention may be applied, while Fig. 2 shows the circuits disclosingapplicants invention applied to the system ofthe above-mentionedcopending application.

Referring now to the drawing and particularly to Fig. l a shortdescription will be made in connection therewith to clearly establishhow the applicants invention may be applied in the system disclosed inthe above-mentioned application. For a full description of -this systemreference may be had to the specication and drawings in theabove-mentioned application.

This switching plan as far as the invention is vconcerned discloses calloriginating crossebar line switches 5 with a group of subscribers linesterminating therein as calling lines and indicated by Vertical lines.There is also shown call terminating cross-bar line switches 6 in whichthe same group of subscribers lines terminate as called line andindicated by Vertical lines. The switches and 6 are interconnected by alinking system comprising links 1 appearing as horizontal lines inswitches 5 and leading into secondary cross-bar switches 8 where theyappear as vertical lines and links or junctors 9 appearing as horizontallines in switches 8 and E. The links 1 also appear as horizontal linesin the recorder switch IU where they may be connected to recorders, oneof which is indicated at I I and appears in the recorder switch as avertical line. A common marker circuit indicated at I2 may be employedas control, means for establishing of connections between lines. Ingeneral such a connection may be established in the following manner:When, for example, the

connects it to the link in the group 1 to which the calling subscribersline is connected and also connects this junctor to the called line, forexample, line I4, through the switches 6. A further description inregard to the ringing and completing of the connection between thesubscribers appears to be unnecessary as far as the present invention isconcerned except to point out that when the calling subscribers line I3is connected to a link in the group 1 and associated select magnet, suchas I5, for example for the rst link, would operate followed by theoperation of the holding magnet for line I3, such as magnet I6, toestablish the connection through switches 5. In the switches 6 wherethis line I3 also appears the holding magnet such as I1 for this linewill also be operated. This is possible as it will be observed that theselect magnet for connecting this line through switches 6 is notoperative at this time. Consequently,

no harm is done by having the two holding magrying out the applicantsinvention. Referring now to Fig. 2 a description will be made of theoperation of the system with respect to the locking-out of the callingsubscribers line in case he fails to dial within a certain period oftime after the dial tone has been received or fails to complete thedialing during this period.

This Fig. 2 shows a subscribers line 20 terminating in a calloriginating switch CO through which a connection from line 2D as thecalling line may be established over contacts at the cross-point 2I bythe operation of the select magnet 22 and the holding magnet 23 to alink 24 for the extension of a connection as described in connectionwith Fig. 1 and according to the system disclosed in the above-mentionedapplication. If the line is a called line the connection may beestablished thereto over contacts at the cross-point 25 in the callterminating switch TI by the operation of select magnet 26 land theholding magnet 21 from a junctor 28 in accordance with the system asdisclosed in the above-mentioned application.

It should be understood that the operations of the circuits shown inthis figure should be considered in connection with the abovedescription relating to Fig. 1 and with the disclosure in theabove-mentioned application. Only a suiiicient description willtherefore be included in this application to clearly illustrate thepresent in- Vention and reference may be made for further circuitoperations if desired to the above-mentioned application. To show howboth of the holding magnets 23 and 21 will operate on a call from line20 as the calling line it may be assumed that the subscriber of line 26in initiating a call removes his receiver from the switchhook. Thiscloses a circuit for the operation of the line relay 30 from battery andground through the two windings of this relay and contacts of theholding magnet 23 over the tip-and ring conductors through the loop atthe subscribers station. Relay 30 in operating closes a circuit tobattery from lead 3I over contacts of the holding magnet 21. Thisoperates a relay in the control and marker circuit to cause operationsto identify the calling line, seize the marker circuit, select arecorder and choose an idle link such as 24 for connecting the line 2Bto an idle recorder through the call originating switch CO and therecorder switch. The result of these operations is that the selectmagnet 22 operates over a circuit from ground supplied at the contactsof a relay in the marker circuit to lead 32 through the winding ofmagnet 22 to battery, followed by the operation of the holding magnet 23over a circuit from battery through the winding of magnet 23 to groundsupplied over lead 33 from contacts of a relay now operated in themarker circuit. This connects the calling line at the cross-point 2| inthe call originating switch CO to the link 24. The holding magnet 23 inoperating opens the circuit for the line relay 30 which now releases toopen the circuit for the lead 3|. A pulsing relay 34 in the recorder isnow operated over a circuit closed through the subscribers loop over thetip-and-ring conductors, contacts at the cross-connecting point 2l, link24, through the connection at the recorder switch and the windings ofrelay 34 to battery and ground. This connection also extends to a dialtone source 35 which transmits a dial tone to the calling subscriber sothat the subscriber may begin dialing of the desired number. When thenumber of the called subscribers line has been dialed, including theringing and coin control circuit code digit, and recorded and thecircuits have operated as described in connection with Fig. 1 to selectan idle junctor such as 36 in the group 9 and connected to the link 24through the secondary switch 8, a circuit is closed for the operation ofthe select magnet 31 in the terminating switch T-I from battery, windingof this magnet, lead 38 to ground at the contacts of a relay in themarker circuit. The operation of this select magnet indicates theselection of the idle junctor 36 and this junctor circuit is thenconnected to the called line 39, rst by the operation of the holdingmagnet 40 in the call originating switch CO over lead 4I from battery,winding of this magnet, lead 4I and contacts of a relay in the markercircuit to ground. Magnet 4I) closes an obvious circuit for the holdingmagnet 42 in the terminating switch T-I so that the called subscribersline 39 now is connected through the terminating switch T| at contacts43 and junctor 36 to the link 24 and through contacts 2| to the callingsubscribers liner 20. The marker circuit is then released and theringing of the called subscriber now takes place from a ringing and coincontrol circuit, over a ringing circuit connector switch. When thecalled subscriber answers the ringing circuit is released and theholding magnets 23 and 42 are held over the sleeve lead while themagnets 22 and 31 are released on the release oi the marker circuit.Conversation between the calling subscriber on line 24, and the calledsubscriber on line 39 over the link circuit`24Y and the junctor circuit35 through the secondary switch 8 may new take place.

Returning now to the point where the calling line was connected to thelink 24 by the operation of the holding magnet 23, it should be notedthat the circuit from ground on lead 33 for operating the holding magnet23 is extended over the sleeve circuit, the contacts at the crosspoint2|, contacts of the recorder switch, contacts of an intermediate relaywhich is operated at this time through the windings of relay 44 tobattery causing the operation of this relay which causes the release ofthe select magnet 22 and otherwise prepares the circuits for dialing.The holding magnet 23 and relay 44 are now locked independent of theoriginal operating circuit for this magnet over circuits to ground atcontacts of relay 45. The locking circuitfor relay 44 extends frombattery of relay 44, contacts of the intermediate relay and of relay 44to ground at contacts of relay 45 and the locking circuit for magnet 23extends from battery, contacts at the cross-point 2|, contacts of relay44 to ground at contacts of relay 45.

Therefore if the subscriber on line has failed to dial or failed tocomplete the dialing within a certain interval after the operation ofrelay 44 these locking circuits for the relay 44 and the holding magnet23 will be opened to release this relay and magnet to disable the cir.-

cuit from establishing a connection to a called subscriber by releasingtherecorder and marker circuits and to prevent the calling subscriberfrom initiating a second connection as long as his receiver remains oithe switchhook.

This is accomplished as follows: It should rst be observed that on theoperation of the holding magnet 23 the associated holding magnet 21 inthe call terminating switch TI is operated over an obvious circuit. Nowif this subscriber fails to complete the call within this .certaininterval a timing circuit arrangement is operated bythe operation ofrelay 44. Relay 44, closes a circuit for relay 45 from battery,left-hand winding of this relay, contacts of relays 44, 46, and 41 toground. Relay 45 transfers the holding ground for relay 44 and holdingmagnet 23 to ground at contacts of relay 41. Relay 45 is also lockedover a circuit from battery through .its right-hand winding and contacton this relay, contacts of an intermediate relay and contacts of relay44 to ground. Relay 45 now closes an abvious vcircuit for the operationof rel-ay 46 which locksto ground over contacts of relay 41. Relay 45,in turn, closes an obvious circuit for the operation of relay 48, thisrelay in turn closing an obvious circuit for the operation of relay 41.Relays 46, 41 and 48 are slow in operating to measure the desired timeinterval. When relay 45 operated the operating circuit for relay 45 wasopened and when relay 41 operated the locking circuits for relay 46,magnet 23 and relay 44 were opened causing the release of magnet 23 andrelay 44. Relay 44 in releasing opens a circuit for relay 45 which inreleasing opens the operating circuit for relay 46 which no-w releasescausing the release of relays 48 and 41 in succession. It should beunderstood that the above-mentioned time interval within which thecalling subscriber must complete a connection may be varied. To this endrelays 4S, 41 and 48 which determine this interval may be of anywellknown delayed action type which may be adjusted to suit differentrequirements in this respect. l

The holding magnet 23 in releasing closes the circuit for thereoperation of the line relay 33 and also opens the operating circuitfor the holding magnet 21 but as the line relay operatesA and theholding magnet 21 is slow in releasing relay v33 closes a lockingcircuit for this holding magnet from battery, winding of magnet 21,'contacts of this magnet to ground at contacts of relay 3D. Relay 33 now.in operating also closes a circuit from ground through its contact tothe lead 53 which is the busy test lead to indicate that the callingline is busy. Hence by maintaining of the holding magnet 21 operated thecircuit from battery through contacts of relay 34 to lead 3| is openedat contacts of magnet 21 and thus the initiation of operations toestablish a connection a second time is prevented. This condition of thecircuit now prevails until the calling' subscriber replaces his receiveron the switchhook when the line relay 3@ releases causing the release ofthe holding magnet 21. Thus it will be seen that the holding magnet 21for the call terminating switch T| is employed to prevent a second callfrom being initiated as long as the calling subscribers receiver remainsoir the switchhook.

In regard to revertive calls from one subscriber to another on a partyline, this arrangement operates as follows. When the connection has beenestablished to test the called line it is found busy, due to theconnection over lead 59 being opened. The open condition of lead 5|through contacts of the holding magnet 21 prevents certain relays in themarker circuit from operating to proceed with the functions to establisha connection to the busy line.' Instead the operation `of the holdingmagnet 21 closes a connection to lead 54 directly from ground andcontacts of the holding magnet 23,v contacts of the holding magnet 21,lead 55 to operate a relay in the marker circuit. This relay now causesthe selection and Vconnectionoi an idle ringing and coin control circuitthrough a ringing circuit connector switch to the link 24 and causes theringing of the desired called party over this link 24 in accordance withthe code selected. When the subscriber answers this code ringing, aringing trip relay in the ringing circuit operates and the establishedconnections are releasedV causing the holding ground over the sleeveconductor through the call originating switch CO to be removed. Magnet23 thereby releases causing the operation of the line relay 34 whichholds the magnet 21 operated as this magnet is slow to release. Theabsence of ground on lead 5i indicating that the line is busy and relay34 and magnet 21 are maintained operated until the subscribers hang upVtheir receivers. Y

What is claimed is:

1. In a telephone system, lines, a call originating switch having aholding magnet for each line, a call terminating switch having a holdingmagnet for each line, said lines appearing in both of said switches,linking circuits, means responsive to a line when calling for operatingsaid originating switch and the holding magnet of both switches for saidcalling line for extending a connection from said calling line to anidle linking circuit, and means for operating said terminating switchfor eastablishing a connection from said seized linking circuit to acalled line and for operating the holding magnets of both switches forsaid called line.

2. In a telephone system, lines, a call originating switch having aholding magnet for each line, a call terminating switch having a holdingmagnet for each line, said lines appearing in both of said switches,linking circuits, means responsive to a line when calling for operatingsaid call originating switch and the holding magnet of both switches.for said calling line for extending a connection from said calling lineto an idle linking circuit, means for operating said terminating switchto extend a connection from said seized linking circuit to a called lineand causing the operation of the holding magnet of the called line inthe call terminating switch to operate by rst causing the associatedholding magnet in the call originating switch to operate.

3. In a telephone system, lines, linking circuits, cross-bar switchesfor extending connections between a calling line and a called line overa 4linking circuit and including a holding magnet for holding aconnection over a call originating switch from a calling line to alinking circuit and a holding magnet for holding a connection over acall terminating switch from Aa linking circuit to a called line, meansresponsive to the seizure of a calling line for connecting said callingline to an idle linking circuit over a call originating switch andoperating the holding magnet in said call originating switch and inresponse to the operation of said magnet for operating the holdingmagnet in the associated call terminating switch for said calling line,and means responsive to dial pulses received from the calling line forconnecting a called line to the seized linking circuit over a callterminating swit-ch and for operating the holding magnet of theassociated call originating switch and in response to the operation ofsaid holding magnet for operating the holding magnet in the said callterminating switch.

4. In a telephone system, an originating switch, a terminating switch, aline appearing in both of said switches, means responsive to said linewhen calling for operating said originating switch to extend aconnection from said line, means for operating said terminating switchto extend a connection to said line when called, means effective whilesaid line is in a calling condition for releasing said originatingswitch to release the connection extended from said line, and meansincluding said terminating switch for preventing said calling line fromcausing the reoperation of said originating switch.

5. In a telephone system, an originating switch, a terminating switch, aline appearing in both of said switches, a line relay individual to saidline and normally connected thereto, means controlled by said relay whensaid line is calling for operating said originating switch to extend aconnection from said line, means for disconnecting said relay from saidline, means for operating said terminating switch to extend a connectionto said line when called, means for releasing said originating switch torelease the cennection extended from said line and for reconnecting saidline relay to the line, and means including said terminating switch forpreventing said line relay from causing the reoperation of saidoriginating switch.

6. In a telephone system, an originating switch having an operatingmagnet, a terminating switch having an operating magnet, a lineappearing in both of said switches, a line relay individual to said lineand normally connected thereto, means responsive to the operation ofsaid line relay when said line is calling for causing the operation ofthe magnet of said originating switch to extend a connection from saidline and to disconnect said line relay from said line, means foroperating the magnet of said terminating switch to extend a connectionto said line when called, means for releasing the magnet of saidoriginating switch to release the connection extended from said line andto reconnect the line relay to said line, and means controlled by themagnet of said terminating switch for preventing the reoperation of theline relay from initiating the reoperation of said originating switch.

7. In a telephone system, lines, linking circuits, cross-bar switchesfor extending connections between a calling line and a called lino overlinking circuits and including a holding magnet for holding a connectionover a call originating cross-bar switch from a calling line to alinking circuit and a holding magnet for holding a connection over acall terminating crossbar switch from a linking circuit to a called lineand in which all lines terminate in both the call originating and callterminating switches, means responsive to the seizure of a calling linefor connecting it to an idle linking circuit over a call originatingswitch and operating both associated holding magnets, means responsiveto dial pulses received from said calling line for connecting a calledline to the seized linking circuit over a call terminating cross-harswitch and operating both associated holding magnets, and meanscontrolled by the two first mentioned holding magnets when theconnection is established from the calling line to a linking circuitover the call originating switch for releasing said call originatingswitch to release said linking circuit from the calling line if theconnection to the ycalled line is not completed within a certaininterval after the connection was extended from the calling line to saidlinking circuit and for preventing the reoperation of said calloriginating switch to seize another linking circuit by the calling line.

8. In a telephone system, lines, linking circuits, cross-bar switchesincluding a call originating line switch for extending connections froma calling line to a linking circuit and a call terminating line switchfor extending connections from a linking circuit to a called line, saidswitches also including selecting magnets for selecting linking circuitsand holding magnets for selecting calling lines and called lines in saidtwo types of switches respectively, means operative on the seizure of acalling line for operating a select magnet in the call originatingswitch and the holding magnet for the calling line in said calloriginating switch and the helding magnet in the corresponding callterminating switch for seizing a linking cirmiit in said calloriginating switch, means responsive te dial pulses received over thecalling line for operating a select magnet in the call terminatingswitch and the holding magnet of the call line in the call originatingswitch and the holding magnet in the corresponding call terminatingswitch for establishing a connection between a seized linking circuitand the called line, a permanent signal arrangement operative in casethe calling line subscriber fails to complete the connection to a calledline within a certain time interval after the connection has extendedthrough the call originating switch to a linking circuit, saidarrangement being controlled -by the two operated holding magnets torelease the call originating switch and to prevent the callingsubsscribers line from initiating another call.

9. In a telephone system, lines, linking circuits, cross-bar switchesincluding call originating line switches for extending connections fromcalling lines to linking circuits and call terminating line switches forextending connections from linking circuits to called lines, saidswitches also including selecting magnets for selecting linking circuitsand holding magnets for selecting calling lines and called lines in saidtwo types ci switches, respectively, means operative on the seizure of acalling line for operating a select magnet in a call originating switchand the holding magnet for the calling line in said call originatingswitch and the holding magnet in the corresponding call terminatingswitch for seizing a linking circuit in said call originating switch,means responsive to dial pulses received over the calling line foroperating a select magnet in a call terminating switch and the holdingmagnet of the called line in the corresponding call originating switchand the holding magnet in the corresponding call terminating switch forestablishing a connection between a seized linking circuit and thecalled line, a permanent signal arrangement for releasing the holdingmagnet for the call originating switch to release the calling line fromthe seized linking circuit operative if the calling line subscriberfails to complete the connection to a called line within a certaininterval after the seizure of the linking circuit and means controlledon the release of said holding magnet for maintaining the holding magnetin the corresponding call terminating switch operated and for therebypreventing the calling line from initiating another call.

10. In a telephone system, lines, linking circuits, cross-bar switchesincluding call originating line switches for extending connections fromcalling lines to linking circuits and call terminating line switches forextending connections from linking circuits to called lines, saidswitches also including selecting magnets for selecting linking circuitsand holding magnets for selecting calling lines and called lines in saidtwo types of switches, respectively, a line relay for each line, meansresponsive to the seizure of a calling line for operating thecorresponding line relay, means controlled by said relay when operatedfor operating a selecting magnet in a call originating switch and theholding magnet for said calling line in said call originating switch andthe holding magnet in the corresponding call terminating switch forseizing a linking circut by said call originating switch and forreleasing the line relay when said connection is established, meansresponsive to dial pulses received over the calling line for operating aselect magnet of a call terminating switch and the holding magnet of thecalled line in the corresponding call originating switch and the holdingmagnet in the corresponding call terminating switch for establishing aconnection between a seized linking circuit and a called line, apermanent signal arrangement for releasing the holding magnet for thecall originating switch'to release the calling line from the seizedlinking circuit operative in case the calling line subscriber fails tocomplete the connection to a called line a certain interval after theconnection was extended through the call originating switch to a linkingcircuit, and to reoperate the line relay to maintain the holding magnetof the corresponding call terminating switch operated and for therebypreventing the calling line from initiating another call.

11. In a telephone system, an originating switch, a terminating switch,a party line appearing in both switches, means responsive to said linewhen a party thereon is calling another party on the same line foroperating said originating switch to extend a connection from said lineand causing the ringing code of the called party to be transmitted oversaid connection to the line and means including the terminating switchoperative when the called subscriber answers for releasing saidoriginating switch to terminate the ringing and to release theconnection extending from said line and for preventing said party lineas long as it is engaged by the calling subscriber andcalled subscriberfrom causing the reoperation of said originating switch.

12. In a telephone system an originating switch, a terminating switch, aparty line appearing in both switches, a line relay individual to saidline and normally connected thereto, means controlled by said relay whena subscribed on said line is calling another subscribed on the same linefor operating said originating switch to extend a connection from saidline and to ring said other subscriber and for disconnecting said relayfrom said line, means for releasing said originating switch to releasethe connection extended from said line to stop the ringing and connectsaid line relay to the line when the called subscriber answers, andmeans including said terminating switch for preventing said line relayfrom causing the reoperation of said originating switch.

13. In a telephone system, an originating switch, a terminating switch,lines appearing in both. switches, some of said lines being party lines,means responsive to a call from any one of said lines for operating saidoriginating switch to extend a connection from said line and foryoperating said terminating switch to extend a connection to a singleline when called, means operated when a subscriber on a party line iscalling another subscriber on said party line for ringing said otherparty over the connection extended through said originating switch,means eiective while a single line is in calling condition or when thecalled subscriber answers on a call from one subscriber to another on aparty line for releasing the originating switch, and means including theterminating switch for preventing the subscriber of the calling line orthe calling subscriber and called subscriber on 'a party line fromcausing the reoperation of the originating switch.

14. In a telephone system, an originating switch, a terminating switch,lines appearing in both of said switches, some of said lines being partylines, line relays individual to each line normally connected thereto,means controlled by a line relay when a single line is calling tooperate said originating switch to extend a connection from said line,means controlled by a line relay when the subscriber on a party line iscalling another subscriber on the same line for operating saidoriginating switch to extend a connection from said party line andcausing the ringing code of the called party on said party line to betransmitted back over said connection from the party line through' thecall originating switch, means for disconnecting a line relay from aline whether it is a single or a party line, means for releasing saidoriginating switch to release the connection from a calling line when itis a single or a party line and means including said terminating switchfor preVenting a line relay of a single or a party line from causing thereoperation of said originating switch.

15. In a telephone system, lines, some of which are party lines, a calloriginating switch having a holding magnet for each line, a callterminating switch having a holding magnet for each line, said linesappearing in both of said switches, linking circuits, means responsiveto lines when calling for operating said originating switch and theholding magnet of both switches for extending a connection from saidcalling to an idle linking circuit, means for operating said terminatingswitch for establishing a connecs,

tion from said seized linking circuit to the subscriber on a called lineif the subscriber on said called line is not on th'e same line as thesubscriber on the calling line and for operating the holding magnet ofboth switches for said called line, means operative if a calledsubscriber is on the same party line as the calling subscriber when saidline is calling for operating the call 'originating switch and theholding magnets of both switches to extend a connection to an idlelinking circuit and causing the ringing code of the called subscriber onsaid party line to be transmitted back over said seized linking circuitthrough the call originating switch to the party line, means operatedwhen the called party line subscriber answers, and for releasing saidconnection to an idle linking circuit by the release of the holdingmagnet in the call originating switch and for holding the holding magnetof the call terminating switch operated to prevent the reoperation ofthe call originating switch until the calling subscriber and the calledsubscriber on said party line releases the connection and meansoperative if the calling subscriber fails to complete a call forreleasing the connection to an idle linking circuit by the release ofthe holding magnet on the call originating switch and for holding theholding magnet of the called terminating switch operative to prevent thereoperation of the call originating switch until the calling subscriberreleases the connection EDSON L. ERWIN.

